This is a question because there were several Sabbaths honored by the Jews. The seventh day Sabbath stated in the Ten Commandments (Exodus 20:8-10) is only one type of Sabbath. For example the first and last days of The Feast of Unleavened Bread (Nisan 15 and Nisan 21) are both Sabbaths (Lev 23:5-8). Rosh Hashanah (Feast of Trumpets) and Yom Kippur (Day of Atonement) are also both Sabbaths. These types of Sabbaths are related to the day of the month, NOT the day of the week. In other words, ALL Sabbaths besides the Seventh day Sabbath are unrelated to days of the week. The Seventh day Sabbath, of course, always lands on Saturday.

With this in mind, which Sabbath day were the Jews concerned about? Which one was pending as they were burying Jesus?

"And behold, a man named Joseph, who was a member of the Council, a good and righteous man (he had not consented to their plan and action), a man from Arimathea, a city of the Jews, who was waiting for the kingdom of God; this man went to Pilate and asked for the body of Jesus. And he took it down and wrapped it in a linen cloth, and laid Him in a tomb cut into the rock, where no one had ever lain. And it was the preparation day, and the Sabbath was about to begin. Now the women who had come with Him out of Galilee followed after, and saw the tomb and how His body was laid. And they returned and prepared spices and perfumes. And on the Sabbath they rested according to the commandment (this would be a seventh day Sabbath). But on the first day of the week (Sunday), at early dawn, they came to the tomb, bringing the spices which they had prepared." (Luke 23:50-24:1) parenthesis added.

The phrase "preparation day", is a significant one. According to the International Standard Bible Encyclopedia:

"The word occurs with technical significance ("the Preparation") in the gospel narratives of the crucifixion, translating the Greek [paraskeue] (Mt 27:62; Mk 15:42; Lk 23:54; Jn 19:14, 31, 42). It is used as a technical term indicating the day of the preparation for the (seventh day) Sabbath, that is, the evening of Friday. This is its use in Josephus, Ant, XVI, vi, 2, and presumably in the Synoptics. Later its use seems to have been extended to denote regularly the 6th day (Friday) of each week. So in the Didache, viii and the Martyrdom of Polycarp, vii."

To summarize the passage above in Luke, the women went to the grave to view the body of Jesus on the preparation day (Friday evening before 6pm) and then rested according to the 4th Commandment, on the Saturday Sabbath. When the Saturday Sabbath had past, the women returned to the tomb at sunrise, and that day was the first day of the week (Sunday). Clearly then, Jesus was crucified on Friday afternoon, the preparation day for the Saturday Sabbath. Additional support can be added from the gospel of John.

"The Jews therefore, because it was the day of preparation, so that the bodies should not remain on the cross on the Sabbath (for that Sabbath was a high day), asked Pilate that their legs might be broken, and that they might be taken away." (John 19:31)

This seems to indicate that there was something different about that Sabbath. Literally, this says it was a great Sabbath, one of unique importance. It wasn't just another Saturday. The logical conclusion is that the Feast of Unleavened Bread fell on the Sabbath this year. It would NOT be logical to call Passover or the Feast alone a "high" Sabbath, because these events can never coincide with one another. They can only coincide with the seventh day Sabbath.